DDJ-RB Crossfader not working

How do you assign a channel to the crossfader? I have a DDJ SB3 having the same issues as the person who has the RB model. Also, my channel levels aren't working either. I cannot lower the volume with the channel levels for some reason.

@Omar > On the SB3 it's automatically assigned unless you've disabled the crossfader in the Serato DJ preferences.

If the channel faders aren't working properly, your SB3 may not be receiving adequate power from your computer; please try another USB cable or a different USB port on the computer.